Climate Change and Food SupplyHave we understood the links?

1. Where do the Food Insecure live?

2. Projections of climate at the end of the 21st Century

3. Climate Change and food security in developing nations

David S. Battisti

Univ. of Washington

Where do the Food Insecure live?

What do the foodinsecure eat?

• Rice (26%)

• Wheat (17%)

• Sugar Cane (8%)

• Maize (6%)

• Nuts (5%)

• Casava (4%)

• Other (34%)

940 M people are malnourished today

• 95% are in the tropics/subtropics

The food insecure are also the poor. They depend heavily

on agriculture for both food an income.

Lobell et al (2008)

Climate Change and Food SupplyHave we understood the links?

1. Where are do the Food insecure live?

2. Projections of climate at the end of the 21st Century

(from IPCC)

– Focus on those changes that are “very likely” (i.e.,

those that are either deemed to have a greater than

90% chance to occur “based on quantitative analysis

or an elicitation of the expert views”)

3. Climate Change and food security in developing nations

How much Carbon Dioxide will be

released into the atmosphere?

A1B

A2 (business

as usual)

B1 (utopia)

Estimates depends on population and economic projections, future choices

for energy, governance/policy options in development (e.g., regional vs.

global governance)

A1B

A2

B1

Emissions

Projected Annual Average Surface

Temperature Change:

“2080-2099” minus “1980-1999”

Average of 21 climate models forced by Scenario A1B.

Multiply by ~1.2 for A2 and ~0.7 for B1

Projected Annual Average Precipitation:

“2080-2099” minus “1980-1999”

Scenario A1B

Stippling is where the multimodel average change exceeds the standard deviation of the models

There is a robust drying of the subtropics, 20-35N&S.

WetterDrier

Climate changes due to human activity

Virtually certain > 99%

Very likely >90%

IPCC 2007

Climate Change and Food SupplyHave we understood the links?

1. Where are do the Food insecure live?

2. Projections of climate at the end of the 21st Century

3. Climate Change and food security in developing nations

Projected Changes in the Central Asia:

“2080-2099” minus “1980-1999”

Scenario A1B

Drying in Central Asia and Southern Europe

(~ 10 - 25% reduction of annual mean precip)

Dec-Feb June-Aug

The recent 1998-2001 drought in the Central Asia

~ 30%

annual

mean

precip

deficit

Pre

cip

Anom

aly

(mm

/month

)

1950 200019901970

- 20

20

0

The recent 1998-2001 drought in

the Central Asia

•Iran: 80% of livestock lost

35 - 75% reduction in wheat & barley

•Afghanistan: 40% of livestock lost

•Pakistan: 50% of livestock lost

•Tajikistan: 50% of grain crop lost

By the end of the century, similar water stress on agriculture will

be the norm throughout the tropics and subtropics due to the

climate changes associated with increasing CO2.

Projections of future temperature

Mean

1900-2000

Mean

2070-2100

Probability

Temperature

Projected Annual Average Surface

Temperature Change:

“2080-2099” minus “1980-1999”

Average of 21 climate models forced by Scenario A1B.

Multiply by ~1.2 for A2 and ~0.7 for B1

Extreme Heat in Western Europe in 2003:

JJA temperature 3.6°C above normal

•France & N. Italy: 30,000 - 50,000 dead of heat stress

•Italy: 36% drop in maize yields

•France: 30% decrease in maize and fodder production

25% decline in fruit harvests

21% reduction in wheat yields

By 2100, years of similar temperature stress on agriculture will

be the norm throughout the tropics and subtropics due to the

summer average temperature changes.

Refs: UNEP 2007; Easterling 2007; Earth Policy Institute 2006; Eurosurveillence 2005

Growing Season Temperature

2003

France

Observed JJA Temp

(1900-2007)

Projections of Growing Season Temperature

Projections use 22

climate models (IPCC

AR4) forced by A1B

Emission scenario.

Variability taken from

observations

Observed JJA Temp

(1900-2007)

2003

France

Projections of Growing Season Temperature

The Sahel

2003

France

Projections of Growing Season Temperature

By the end of the 21st Century it will be much hotter everywhere

In most of the tropics/subtropics, the seasonal average

temperature will very likely exceed the warmest year on record

Battisti and Naylor 2008

Impacts of Climate Change on Food Security

Increasing temperature over the

next 50 years will cause decreases

in yield:

• Decrease in grain filling

• Decrease in spikelet fertility

• Increased water stress

• Increased respiration

Important for all crops, but

especially for wheat, rice and

soybeans (nb, these are the C3

crops that would otherwise benefit

from increased CO2) and maize

Lobell 2007

Wheat Yield in Yaqui

Valley, MX

Jan-Mar Night Temp (°C)

• Reduced yields of wheat, rice and soybeans in the

tropics/subtropics

– Approximately -10% per 1ºC warming

– Est. reduction of 30-40% by 2100 in India, Southern Africa,Middle East, etc.

• Reduced nutritional content (especially protein in wheat

and rice)

• Increased disease transmission rates

• Loss of water stored in snow pack and glaciers (e.g.,

Sierra, Himalaya)

– Reduced duration of river supplied water, especially important

for India and Bangladesh

Impacts of Climate Change on Food Security

Impacts of increased temperature (only):

Impacts of Climate Change on Food Security

By 2050, many countries in the subtropics will experience:

– Typically a 10 - 20% reduction in rainfall (northern and southern

Africa, Caribbean, Middle East, etc.)

– Increased frequency, duration and intensity of drought

– Increased flooding in midlatitudes and tropics (increase intensity

of precipitation on drier soils

– Reduced yields and in some places abandonment of staple

crops (many of these regions are marginal for crops presently

grown)

– Leaching of nutrients in soil

Impacts of changing precipitation:

Impacts of Climate Change on Food Security

• Changes in pest and pathogens (yet unknown)

• Increased carbon dioxide and plants

– Enhanced growth rate for some C3 plants (benefits limited

to < 2030AD, and to the extratropics)

– Including temperature increases due to CO2, a net negative

impact in tropics/subtropics for all crops (C3 and C4)

– Effects on soil BGC

– Effects on plant pathology (reduced protein content and

resilience to disease)

• Sea level rise: about 35cm by 2100

– salinization and loss of arable land

Other impacts of climate change on agriculture

Summary: World-wide impact on Crops

• By 2100, growing season temperatures will

very likely exceed the warmest on record

throughout the tropics and subtropics

– 30-40% reduction in yields of major crops (plant

physiology)

• In subtropics, crops will be further stressed by

reduced rainfall

• Increased CO2 (fertilization) effect is small

(~10% for doubling CO2)

• Pest and Pathogens (stay tuned)

Where do the Food Insecure live?

The food insecure - depend heavily on

agriculture for foodand income

- live in regions whereagriculture will bemost stressed byglobal warming

- live in countries thathave the greatestpopulation growthrates

940 M people are malnourished today

• 95% are in the tropics/subtropics

Estimates: 200-400M more people at risk

of hunger by 2080 due to climate change

Lobell et al (2008)